CN111927724A - Design method for heat collection field of partitioned trough type solar thermal power generation system - Google Patents

Design method for heat collection field of partitioned trough type solar thermal power generation system Download PDF

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CN111927724A
CN111927724A CN202010739437.2A CN202010739437A CN111927724A CN 111927724 A CN111927724 A CN 111927724A CN 202010739437 A CN202010739437 A CN 202010739437A CN 111927724 A CN111927724 A CN 111927724A
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heat
collection field
transfer medium
temperature
heat transfer
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CN111927724B (en
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张燕平
王渊静
张�成
刘易飞
王鼎
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Huazhong University of Science and Technology
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03G—SPRING, WEIGHT, INERTIA OR LIKE MOTORS; MECHANICAL-POWER PRODUCING DEVICES OR MECHANISMS, NOT OTHERWISE PROVIDED FOR OR USING ENERGY SOURCES NOT OTHERWISE PROVIDED FOR
    • F03G6/00—Devices for producing mechanical power from solar energy
    • F03G6/06—Devices for producing mechanical power from solar energy with solar energy concentrating means
    • F03G6/065—Devices for producing mechanical power from solar energy with solar energy concentrating means having a Rankine cycle
    • F03G6/067—Binary cycle plants where the fluid from the solar collector heats the working fluid via a heat exchanger
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
    • G06F2119/08—Thermal analysis or thermal optimisation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/40—Solar thermal energy, e.g. solar towers
    • Y02E10/46—Conversion of thermal power into mechanical power, e.g. Rankine, Stirling or solar thermal engines

Abstract

The invention belongs to the field of solar field design optimization, and particularly discloses a method for designing a heat collection field of a zoned trough type solar thermal power generation system, which comprises the following steps; dividing the solar heat collection field into three areas, namely a high-temperature area heat collection field, a medium-temperature area heat collection field and a low-temperature area heat collection field, supplying heat for different heat exchangers respectively, and establishing a simulation analysis model of the trough type solar heat power generation system according to the layout; establishing an objective function with the maximum total efficiency of the power generation system as an optimization target, determining constraint conditions, and solving the objective function to obtain heat transfer medium parameters; and then the quantity and the layout mode of the heat collectors in the heat collecting fields of all the areas are obtained according to the parameters of the heat transfer medium, and the design of the heat collecting fields of the trough type solar thermal power generation system is completed. The design method of the invention can effectively reduce the average temperature of the heat transfer medium in the heat collecting pipe and reduce the heat exchange end difference of the steam production system, thereby improving the efficiency of the heat collecting field and the total efficiency of the power station.

Description

Design method for heat collection field of partitioned trough type solar thermal power generation system
Technical Field
The invention belongs to the field of solar field design optimization, and particularly relates to a design method of a heat collection field of a zoned trough type solar thermal power generation system.
Background
As the world economy continues to grow, the world energy system will face the dual challenges of "more energy" demand and "lower emissions", with the importance of renewable energy becoming increasingly prominent. The trough type solar photo-thermal power generation technology is more and more high in commercialization level as a large-scale solar photo-thermal power generation technology which is mature and low in cost at present. At present, the trough type solar thermal power station which is put into commercial application in the world, such as SEGS VI series power stations in the United states, has the total installed capacity of 353.8WM and the total efficiency of 14-18 percent; the installed capacity of an Andasol series power station of Spain is 50MW, and the total efficiency of the power station is 13.5%; installed capacities of Noor1 and Noor2 groove type photo-thermal power stations in the Morocco Noor photo-thermal power generation complex respectively reach 160MW and 200MW, installed capacities of Ashalim 2 groove type photo-thermal power stations in Israel reach 121MW, but the total efficiency of the power stations is still 11% -16%.
In the conventional trough-type solar thermal power generation system, at the heat collection field
Figure BDA0002606130630000012
This results in a lower thermal field efficiency and thus makes it difficult to increase the overall system efficiency. The efficiency of the heat collection field is related to the temperature of the heat transfer medium, the higher the temperature of the heat transfer medium is, the lower the efficiency of the heat collector is.
For a traditional groove type solar thermal power generation system, in the process that a working medium is heated from a supercooled liquid to a superheated gas by a heat transfer medium, the mass flow rates of the heat transfer medium and the working medium are not changed, but the working medium is subjected to phase change along with the increase of the temperature, the specific heat capacity difference is large, and the heat transfer medium does not have the heat capacity differencePhase change, small difference of specific heat capacity, large heat exchange temperature difference in the heat exchange process and large generated heat exchange temperature difference
Figure BDA0002606130630000011
And the energy utilization rate is reduced.
Disclosure of Invention
Aiming at the defects or improvement requirements in the prior art, the invention provides a design method of a heat collection field of a sectional groove type solar thermal power generation system, which aims to divide the solar thermal collection field into three regions, respectively correspond to different heat exchangers, establish a mass flow optimization model of each heat collection region by taking the optimal power generation efficiency of a power station as a target, realize the design of a novel sectional heat collection mirror field according to an optimization result, reduce the temperature of a heat transfer medium in the heat collection tube on the premise of ensuring the requirements of the power generation system, reduce the difference of heat exchange ends, and improve the utilization rate of energy so as to improve the efficiency of the heat collection field and the total efficiency of the power station.
In order to achieve the purpose, the invention provides a design method of a heat collection field of a zoned trough type solar thermal power generation system, which comprises the following steps:
s1 a heat collection field in the trough type solar thermal power generation system supplies heat to a working medium in a heat exchanger through a heat transfer medium, and the heat exchanger is divided into a superheater, an evaporator, a preheater and a reheater; the heat collection field is divided into 3 areas: the system comprises a high-temperature region heat collection field, a medium-temperature region heat collection field and a low-temperature region heat collection field, wherein the high-temperature region heat collection field supplies heat for a superheater and a reheater, the medium-temperature region heat collection field supplies heat for an evaporator, and the low-temperature region heat collection field supplies heat for a preheater; establishing a simulation analysis model of the trough type solar thermal power generation system according to the arrangement mode;
s2 analysis model according to simulation, with Mo＝[Mo,1,Mo,2,Mo,3]As decision variables, an objective function with the maximum total efficiency of the power generation system as an optimization target is established as follows:
min f(MO)＝1-ηA(MO)＝1-ηth(MO)*ηhe(MO)
wherein M iso,1,Mo,2,Mo,3The mass flow of the heat transfer medium in the high-temperature zone heat collection field, the medium-temperature zone heat collection field and the low-temperature zone heat collection field respectively; etaAFor the total efficiency of the power generation system, ηthFor the efficiency of the heat collecting field, ηheThe efficiency of thermoelectric conversion;
s3, under the condition that preset constraint conditions are met, solving the objective function by an interpolation method to obtain heat transfer medium parameters, wherein the constraint conditions comprise heat transfer medium temperature constraint, energy conservation constraint and heat transfer medium mass flow constraint; and then the quantity and the layout mode of the heat collectors in the heat collecting fields of all the areas are obtained according to the parameters of the heat transfer medium, and the design of the heat collecting fields of the trough type solar thermal power generation system is completed.
As a further preference, the heat transfer medium temperature constraints are:
Figure BDA0002606130630000031
wherein, To,i,outFor the i-th zone heat collection field outlet heat transfer medium temperature, To,i,inFor the i-th zone collector inlet heat transfer medium temperature, To,i,ave,minAnd i is the minimum value of the average temperature of the heat transfer medium in the ith area, wherein i is 1,2 and 3.
As a further preference, the conservation of energy constraint is:
Figure BDA0002606130630000034
Figure BDA0002606130630000035
wherein M iso,iFor the ith zone mass flow rate of heat transfer medium,
Figure BDA0002606130630000036
Δ T is the specific heat capacity of the heat transfer mediumo,iThe temperature difference, eta, of the heat transfer medium at the inlet and the outlet of the ith zone heat collectorv,iThe heat exchange efficiency corresponding to the ith area; ms,iThe mass flow of the working medium corresponding to the ith area; Δ hs,iThe enthalpy of the working medium corresponding to the i-th zone increases, i is 1,2, 3.
As a advancePreferably, the heat transfer medium mass flow constraint is as follows: 0<Mo,i≤Mo,maxWherein M iso,iFor the i-th zone heat transfer medium mass flow, Mo,maxThe maximum value of the mass flow of the heat transfer medium which occurs during operation is 1,2, 3.
Preferably, the heat transfer medium parameters include mass flow of the heat transfer medium in the high-temperature zone heat collection field, the medium-temperature zone heat collection field, and the low-temperature zone heat collection field, and the temperature of the heat transfer medium at the outlet of each heat exchanger.
Preferably, in S3, the method for calculating the number of collectors in each zone includes the following steps:
(1) calculating the temperature difference delta T of the heat conduction oil at the outlet and inlet of the heat collection field of the ith area according to the obtained parameters of the heat transfer mediumo,iFurther obtaining the temperature difference delta T of heat conducting oil at the inlet and the outlet of each heat collector of the heat collecting field in the areao,ijAnd the temperature drop delta T of the heat collector connecting pipeo,s,ij(ii) a Then obtaining the number of the collectors connected in series in a single row of the ith area
Figure BDA0002606130630000032
(2) According to the rated input power W of the heat collector required by the ith areath,iThermal power delta W of rated output of single-loop heat collectorth,iPower heat loss delta W of connecting pipe with single heat collectorth,p,ijTo obtain the parallel number of the heat collector circuits of the ith area
Figure BDA0002606130630000033
(3) Calculating the number n of heat collectors in the ith area heat collection fielda,i＝ns,inp,iThe total number n of the heat collectors in the whole heat collection fielda＝∑na,i，i＝1,2,3。
Preferably, in S3, when the heat collection field layout manner is determined, the total area of the heat collection field is obtained according to the total number of collectors in the whole heat collection field and the type of the used collector; if the total area of the heat collecting field exceeds 400000m2The heat collecting field adopts H-shaped arrangementIn a mode, if the total area of the heat collecting field is less than 400000m2And the heat collecting field adopts an I-type arrangement mode.
Generally, compared with the prior art, the above technical solution conceived by the present invention mainly has the following technical advantages:
1. according to the invention, according to the energy gradient utilization principle, aiming at the problem of high end difference of a heat exchanger in a conventional groove type solar thermal power generation system, a solar thermal collection field is divided into three areas, the three areas respectively correspond to different heat exchangers, a mass flow optimization model of each thermal collection area is established by taking the optimal power generation efficiency of a power station as a target, and the mass flow of a heat transfer medium of each area is optimized and calculated, so that a better heat transfer medium parameter solution under a novel layout can be obtained, the heat exchange end difference is reduced, the average temperature of the heat transfer medium in the thermal collection tube is reduced, the efficiency of the thermal collection field of each area and the total efficiency of the power station are improved, and the.
2. In the heat collection field adopting the layout mode, the heat conduction oil parameters of all areas can be changed compared with the traditional layout mode, and the relationship between the heat conduction oil temperature and the total efficiency of the heat collection field shows that the reduction of the heat conduction oil temperature can improve the total efficiency of the heat collection field, so that the total efficiency of a power station is improved, and meanwhile, the mass flow of the heat conduction oil is increased; in the actual operation process, the mass flow of the heat transfer medium cannot be infinitely increased, and the invention sets the temperature constraint, the energy conservation constraint and the mass flow constraint of the heat transfer medium pertinently so as to ensure that the obtained result meets the actual condition and ensure that the system can safely operate.
3. The method for calculating the number of the heat collectors connected in series and in parallel in the heat collection fields of all the regions according to the parameters of the heat transfer medium is specifically set, the layout mode of the heat collection fields is further determined, the integral design of the heat collection fields of the groove type solar thermal power generation system is completed, and the practicability is high.
Drawings
FIG. 1 is a schematic diagram of a SEGS VI trough solar thermal power generation system;
FIG. 2 is a schematic structural diagram of a zoned trough-type solar thermal power generation system according to an embodiment of the present invention;
FIG. 3 is a heat collection field layout diagram of the SEGS VI trough type solar thermal power generation system;
FIG. 4 is a layout diagram of a heat collection field of a zoned trough-type solar thermal power generation system according to an embodiment of the present invention;
FIG. 5 is a graph of a heat exchange process in a trough solar thermal power generation system;
FIG. 6 is a graph comparing the average temperature of the SEGS VI system and the system of the embodiment of the present invention;
FIG. 7 is a graph comparing the efficiency of the thermal fields of the SEGS VI system and the system of the present invention;
fig. 8 is a graph comparing the total plant efficiency of the SEGS VI system and the system of the present invention.
The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein: 1-preheater, 2-evaporator, 3-superheater, 4-reheater, 5-high pressure cylinder, 6-low pressure cylinder, 7-generator, 8-condenser, 9-condensate pump, 10-water supply pump, 11, 12-high pressure heater, 13-deaerator, 14, 15, 16-low pressure heater, 17-oil transfer pump and 18-heat collection field.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The embodiment of the invention takes an American SEGS VI trough type solar thermal power plant as an improved object, the structure of a thermal power generation system is shown in figure 1, and the novel layout mode of the invention is adopted for improvement.
The SEGS VI power station uses a heat transfer medium (heat transfer oil) to heat a working medium (water/steam) from supercooled water to superheated steam. On the water/steam side of the working medium, the working components comprise a preheater 1, an evaporator 2, a superheater 3, a reheater 4, a high-pressure cylinder 5, a low-pressure cylinder 6, a generator 7, a condenser 8, a condensate pump 9, a feed pump 10, high- pressure heaters 11 and 12, a deaerator 13 and low- pressure heaters 14, 15 and 16; on the side of the heat transfer oil, the working components of the heat transfer oil pump comprise a fuel delivery pump 17 and a heat collection field 18; wherein:
the superheater 3 is connected with the high-pressure cylinder 5, the exhaust of the high-pressure cylinder 5 is connected with the inlet of the reheater 4, and the outlet of the reheater 4, the low-pressure cylinder 6, the condenser 8, the condensate pump 9, the low-pressure heater 16, the low-pressure heater 15, the low-pressure heater 14, the deaerator 13, the high-pressure heater 12, the high-pressure heater 11 and the water feed pump 10 are sequentially connected; the high-pressure cylinder 5 is respectively connected with high- pressure heaters 11 and 12; the low-pressure cylinder 6 is respectively connected with a deaerator 13 and low- pressure heaters 14, 15 and 16; the generator 7, the low-pressure cylinder 6 and the high-pressure cylinder 5 are connected in sequence.
Specifically, in fig. 1, 2a is a superheater water side outlet and a high pressure cylinder inlet, 2b is a low pressure cylinder outlet, 2c is a high pressure cylinder extraction, 2d is a condenser outlet, 2e is a condensate pump outlet, 2f is a feed pump inlet, 2g is a preheater water side inlet, 2h is a preheater water side outlet and an evaporator water side inlet, and 2i is an evaporator water side outlet and a superheater water side inlet; 3a is a heat conduction oil outlet in the heat collection field, 3b is a superheater heat conduction oil side outlet and an evaporator heat conduction oil side inlet, 3c is an evaporator heat conduction oil side outlet and a preheater heat conduction oil side inlet, and 3d is an oil delivery pump inlet.
When the SEGS VI power station works, water is in a liquid state in the preheater 1, is in a vapor-liquid two-phase state in the evaporator 2, is in a vapor state in the superheater 3, and has a large specific heat capacity difference; the heat transfer oil is in a liquid state in the preheater 1, the evaporator 2 and the superheater 3, and the specific heat capacity thereof is not greatly different, which results in a great temperature end difference between the water inlet of the preheater 1 and the water outlet of the evaporator 2.
According to the invention, the SEGS VI power station is improved to obtain the partitioned trough type solar thermal power generation system, as shown in fig. 2, the working process and the working state of the working medium side are the same as those of the SEGS VI power station, and the heat collection field is only divided into three areas, namely a high-temperature area heat collection field, a medium-temperature area heat collection field and a low-temperature area heat collection field.
Specifically, in fig. 2, 3a is a heat conduction oil outlet of a heat collection field in a high temperature region, 3b, s is a heat conduction oil side outlet of a superheater, 3b, e is a heat conduction oil outlet of a heat collection field in an intermediate temperature region and a heat conduction oil side inlet of an evaporator, 3c,3 are a heat conduction oil inlet of a heat collection field in an intermediate temperature region and a heat conduction oil side outlet of an evaporator, 3c, p are a heat conduction oil outlet of a heat collection field in a low temperature region and a heat conduction oil side inlet of a preheater, and 3d is a heat.
When the partitioned trough-type solar thermal power generation system works, heat conduction oil with different mass flow rates respectively flows through the preheater 1, the evaporator 2, the superheater 3 and the reheater 4, wherein a first flow of heat conduction oil respectively passes through the superheater 3 and the reheater 4 after collecting solar energy in a heat collection field of a high-temperature area, and then returns to the heat collection field of the high-temperature area together; the second heat conduction oil passes through the evaporator 2 after collecting solar energy in the heat collection field of the intermediate temperature region and then returns to the heat collection field of the intermediate temperature region; the third heat conduction oil is collected in the low-temperature zone heat collection field, passes through the preheater 1 and then returns to the low-temperature zone heat collection field. The feed water is heated to superheated steam through a preheater 1, an evaporator 2 and a superheater 3 in sequence, one steam enters a high-pressure heater 11 and a high-pressure heater 12 respectively after entering a high-pressure cylinder 5, one steam is used for pumping air and passes through a reheater 4 and a low-pressure cylinder 6, the steam in the low-pressure cylinder 6 does work and then is divided into a plurality of strands, four strands of steam are used for pumping air and enter a deaerator 13, a low-pressure heater 14, a low-pressure heater 15 and a low-pressure heater 16 respectively, and one strand of steam sequentially passes through a condenser 8, a condensate pump 9, a low-pressure heater 16, a low-pressure heater 15, a low-pressure heater 14, the deaerator 13, the high-.
According to the setting mode, the heat collection field of the segmented trough type solar thermal power generation system is further specifically designed, and the method comprises the following steps:
s1, establishing a simulation analysis model of the trough type solar thermal power generation system.
According to the system structure and the operation data of the partitioned trough-type solar thermal power generation system, a simulation analysis model of the trough-type solar thermal power generation system is established by utilizing modeling software so as to determine the relation between the total system efficiency and the temperature of the heat transfer medium and establish a target function.
Specifically, the main input parameters of the simulation analysis model include: 1) environmental parameters: DNI, angle of incidence, wind speed, atmospheric temperature, 2) water/steam side related parameters: main steam flow Ms,iMain steamingThe steam temperature, the main steam pressure and the reheat steam temperature, and the enthalpy rise delta h of each heat exchange processs,i. The output parameters of the simulation analysis model comprise: 1) water/steam side related parameters: inlet water/steam temperature of each heat exchanger, 2) heat transfer oil side related parameters: mass flow of heat conducting oil in each area, temperature of heat conducting oil at outlet of each heat exchanger, and 3) performance parameters: generating power, heat collection field efficiency and total efficiency of the power station.
S2 establishing efficiency eta of heat collection fieldthThe computational model of (1).
The heat collection field is used as a core part of the solar photo-thermal power generation system, and the function of the whole process is to realize the conversion from solar energy to heat energy of a heat transfer medium. In the process of converting solar energy into heat energy of a heat transfer medium, three processes of reflection, penetration and absorption occur, and the efficiency of the heat collection system can represent the conversion efficiency of converting solar energy into heat energy of the heat transfer medium. According to the heat transfer process, at a certain moment, the solar radiation intensity I of each heat collector in the same system can be considered to be equal, Q is the heat quantity effectively absorbed by the heat transfer medium in the whole heat collection field, and the calculation mode is as follows:
Figure BDA0002606130630000071
wherein M iso,iFor the mass flow of heat transfer medium, Δ T, in the i-th zone collectoro,iThe temperature difference of the heat transfer medium at the inlet and the outlet of the ith area heat collection field,
Figure BDA0002606130630000081
the specific heat capacity of the heat transfer medium in the ith zone. Thereby the photo-thermal conversion efficiency eta of the heat collection fieldthCan be characterized as:
Figure BDA0002606130630000082
wherein S is the opening area of the reflector surface of the heat collector in the heat collection field. .
In order to determine the influence of the temperature of the heat transfer medium on the photothermal conversion efficiency of the heat collector, the data acquired by an actual operation test of the LS-2 type heat collector and a relational expression eta between the atmospheric temperature and the average temperature difference of the heat transfer medium and the measured value of the photothermal conversion efficiency of the heat collector are referredth＝73.1+0.00120(dT)-0.0000850(dT)2And dT is the difference between the atmospheric temperature and the average temperature of the heat transfer medium. From the relational expression, it can be known that the photothermal conversion efficiency of the heat collector tends to be gradually reduced with the increase of the difference between the atmospheric temperature and the average temperature of the heat transfer medium, and therefore, the temperature of the heat transfer medium should be kept as low as possible in the optimization process. The relation is calculated under the condition of an incident angle of 0 degrees, only the relation between the temperature of the heat transfer medium and the photothermal conversion efficiency of the heat collector is shown, and the relation is not suitable for conventional calculation, so that a more general calculation formula of the photothermal conversion efficiency of the heat collector is adopted:
Figure BDA0002606130630000083
Figure BDA0002606130630000084
in the formula etaoptThe value of the optical efficiency of the heat collector is 73.3 percent, and K isτaThe correction coefficients of incidence angle, a, b and c are all thermal equilibrium coefficients, and the value of a is 1.9182 × 10-2WK-1m-2,b＝2.02*10-9WK-1m-2,c＝6.612*10-3WK-1m-2，VwindIs the ambient wind speed, Tav,ijIs the average temperature T of the heat transfer medium in the heat collecting field of the ith regionaIs at the temperature of the surroundings and is,abemissivity of the absorber tubes, TskyThe sky temperature is typically 0 ℃, i ═ 1,2, 3.
S3 establishing thermoelectric conversion efficiency etaheThe computational model of (1).
After being heated, the heat transfer medium in the heat collection field enters the heat exchange system to transfer heat to the working medium, and the working medium converts the heat energy into electric energy through the working process. The efficiency of the process of finally converting the heat energy of the heat transfer medium into the electric energy is defined as the thermoelectric conversion efficiency and the calculation mode is given:
Figure BDA0002606130630000085
wherein P iseThe total output power of the power station and Q are the heat quantity effectively absorbed by the heat transfer medium in the whole heat collection field, and the calculation mode is as follows:
Figure BDA0002606130630000086
s4 establishing the total efficiency eta of the power stationAThe computational model of (1).
In the solar thermal power generation system without the heat storage system, the energy conversion process is that solar energy is converted into electric energy, so that the expression is
Figure BDA0002606130630000091
From each subsystem, the energy conversion process can be divided into two processes of converting solar energy into heat energy and converting heat energy into electric energy, so that the total efficiency formula of the power station can also be written as
Figure BDA0002606130630000092
Therefore, the total efficiency of the power station can be jointly calculated by the efficiency of the heat collection field and the thermoelectric conversion efficiency.
S5, establishing an objective function of the heat transfer oil mass flow optimization model with the optimal power station efficiency as the target.
In the heat collection field adopting the novel layout mode, the heat conduction oil parameters of all the areas can be changed compared with the traditional layout mode. According to the relation between the temperature of the heat conduction oil and the total efficiency of the heat collection field, the total efficiency of the heat collection field is improved by reducing the temperature of the heat conduction oil, so that the total efficiency of a power station is improved, and meanwhile, the mass flow of the heat conduction oil is increased. Thus with Mo＝[Mo,1,Mo,2,Mo,3]As decision variables, an objective function with the maximum total efficiency of the power generation system as an optimization target is established as follows:
min f(MO)＝1-ηA(MO)＝1-ηth(MO)*ηhe(MO)
wherein M iso,1,Mo,2,Mo,3The mass flow of the heat transfer medium in the high-temperature zone heat collection field, the medium-temperature zone heat collection field and the low-temperature zone heat collection field respectively; etaAFor the total efficiency of the power generation system, ηthFor the efficiency of the heat collecting field, ηheThe thermoelectric conversion efficiency. In the actual operation process, the mass flow of the heat transfer oil cannot be infinitely increased, so that the heat transfer oil still needs to be fullWhich is sufficient for its constraint.
S6 determines constraints relating to the temperature of the heat transfer medium.
If the efficiency eta of the heat collection field is to be improvedthThe average temperature of the heat transfer medium should be suitably reduced to less than the minimum desirable average temperature of the heat transfer medium. The heat transfer medium temperature constraint can thus be written as:
Figure BDA0002606130630000093
wherein, To,i,outFor the i-th zone heat collection field outlet heat transfer medium temperature, To,i,inFor the i-th zone collector inlet heat transfer medium temperature, To,i,ave,minAnd the minimum value of the average temperature of the heat transfer medium of the heat collection field is the ith area.
S7 determines constraints related to conservation of energy.
When calculating the parameters of the heat transfer medium in each area of the improved system, besides ensuring that the average temperature of the heat transfer medium is low, the heat exchange process is ensured to follow the first law of thermodynamics, so that the constraint condition related to energy conservation can be obtained:
Figure BDA0002606130630000101
wherein M iso,iFor the ith zone mass flow rate of heat transfer medium,
Figure BDA0002606130630000102
Δ T is the specific heat capacity of the heat transfer mediumo,iThe temperature difference, eta, of the heat transfer medium at the inlet and the outlet of the ith zone heat collectorv,iThe heat exchange efficiency corresponding to the ith area; ms,iThe mass flow of water/steam corresponding to the ith zone; Δ hs,iThe water/steam enthalpy for the ith zone increases.
S8 determines constraints relating to the heat transfer medium mass flow.
In order to ensure the safe operation of the system adopting the novel layout mode and limit the maximum value of the flow, the constraint conditions of the mass flow of the heat transfer medium are as follows: 0<Mo,i≤Mo,maxWherein M iso,iMass flow of heat transfer medium for the i-th zone，Mo,maxIs the maximum mass flow of the heat transfer medium that occurs during operation.
S9 determines the heat transfer medium parameter.
Under the premise of meeting constraint conditions and actual operation conditions, performing iterative computation on the parameters of the heat transfer medium in the objective function by adopting an interpolation method to obtain an optimal solution; the heat transfer medium parameters comprise mass flow of heat transfer media in the high-temperature zone heat collection field, the medium-temperature zone heat collection field and the low-temperature zone heat collection field, and the temperature of the heat transfer media at the outlet of each heat exchanger.
S10, establishing a heat collector quantity calculation model.
(1) Calculating the serial quantity of the heat collectors in each area, and calculating the temperature difference delta T of the heat-conducting oil at the outlet and inlet of the heat collecting field of the ith area according to the obtained parameters of the heat-conducting mediumo,iFurther obtaining the temperature difference delta T of heat conducting oil at the inlet and the outlet of each heat collector of the heat collecting field in the areao,ijAnd the temperature drop delta T of the heat collector connecting pipeo,s,ij(ii) a Then obtaining the number of the collectors connected in series in a single row of the ith area
Figure BDA0002606130630000103
(2) Calculating the parallel quantity of the heat collectors in each area, wherein the parallel quantity of the heat collectors is related to the total power in a loop of the heat collectors, and the rated input power W of the heat collectors required by the ith area is calculated according to the rated input power W of the heat collectors required by the ith areath,iThermal power delta W of rated output of single-loop heat collectorth,iPower heat loss delta W of connecting pipe with single heat collectorth,p,ijTo obtain the parallel number of the heat collector circuits of the ith area
Figure BDA0002606130630000104
(3) Calculating the number n of heat collectors in the ith area heat collection fielda,i＝ns,inp,iThe total number n of the heat collectors in the whole heat collection fielda＝∑na,i，i＝1,2,3。
S11 determines the layout mode of the heat collection field.
According to the obtained total number of the heat collectors in the whole heat collection field and the model of the used heat collectors, the total area of the heat collection field can be obtained;if the total area of the heat collecting field exceeds 400000m2If the total area of the heat collecting field is less than 400000m, the heat collecting field adopts an H-shaped arrangement mode2And the heat collecting field adopts an I-type arrangement mode.
In this embodiment, firstly, parameters under the design condition of the SEGS VI power station are used for calculation, so as to obtain the setting condition of the heat conduction oil parameters and the arrangement condition of the heat collection field.
The main parameters of the heat conduction oil side of the design working condition are compared, as shown in the table 1 and the table 2, the temperature of the heat conduction oil in the improved system is obviously reduced compared with the simulation value of the original SEGS VI power station, and theoretically, the photothermal conversion efficiency of the heat collector can be improved to a certain extent. As shown in table 3, compared with 800 collectors of the SEGS VI plant, the number of the improved thermal collecting field is reduced by 16 collectors under the condition of ensuring the same total power as the original system, so that the initial cost of the plant can be reduced to a certain extent. The SEGS VI power station and the heat collection field arrangement of the invention are shown in figures 3 and 4.
TABLE 1 comparison of main parameters of heat-conducting oil side under design conditions
Figure BDA0002606130630000111
TABLE 2 Heat transfer oil parameter settings for each heating zone
Figure BDA0002606130630000112
TABLE 3 quantity of collectors in each zone of improved system heat collection field
Figure BDA0002606130630000121
Comparing the end difference and the performance parameters of each heat exchanger under the design working condition, as shown in table 4, the error of the improved system is less than 0.05% when the water/steam side parameters are compared with the simulation value of the original SEGS VI power station under the design working condition, namely, the improved system can meet the power generation requirement of the water/steam side.
Table 5 and fig. 5 are schematic diagrams of comparison of end differences of heat exchangers and temperature curves of water and heat transfer oil in a heat exchange system under design conditions, respectively, and it can be seen that the end differences of the preheater 1, the evaporator 2 and the superheater 3 in the present invention are significantly decreased, and the temperatures of the heat transfer oil in the preheater 1, the evaporator 2 and the superheater 3 are lower than those of the conventional heat exchangers, so that the efficiency of a heat collection field is increased, and the total efficiency of a power station is also increased.
Calculated, as shown in table 6, the system of the present invention has a reduction in the preheater end difference of 51.49 ℃, the evaporator end difference of 1.38 ℃, the superheater end difference of 60.86 ℃ and the reheater end difference of 33.78 ℃ compared to the SEGS VI plant. The efficiency of the heat collection field is improved by 0.52 percent, and the total efficiency of the power station is improved by 0.24 percent.
TABLE 4 comparison of Water/steam side Main parameters for design conditions
Figure BDA0002606130630000122
TABLE 5 comparison of end differences of heat exchangers under designed working conditions
Figure BDA0002606130630000123
Figure BDA0002606130630000131
TABLE 6 comparison of Performance parameters for design conditions
Figure BDA0002606130630000132
And then, calculating by using parameters under the running working condition of the SEGS VI power station to obtain a comparison graph of the average temperature and the performance parameters of the heat conduction oil under the working condition.
Fig. 6 is a graph comparing the average temperature of the SEGS VI system and the system of the present invention, and it can be seen that there is a significant decrease in the average temperature of the system of the present invention. Through calculation, the average temperature of the heat conducting oil of the heat collecting field under the operating condition is reduced by 12.97 ℃. According to the characteristics of the heat collector, the average temperature of the heat conduction oil is in negative correlation with the efficiency of the heat collector, so that the efficiency of a heat collection field is improved to a certain extent theoretically.
FIG. 7 is a comparison graph of the heat collecting field efficiency of the SEGS VI system and the system of the invention, the heat collecting field efficiency is improved to some extent due to the reduction of the average temperature of the heat conducting oil, and the heat collecting field efficiency under the operation condition is improved by 0.53% through calculation.
Fig. 8 is a comparison graph of total efficiency of the SEGS VI system and the power station of the system of the present invention, and it can be seen that from 9:00 to 17:00, the system is in a steady operation state, the trend of total efficiency change of the power station before and after improvement is the same, and the improved system is significantly improved compared with the total efficiency of the SEGS VI power station. Through calculation, the total efficiency of the power station in the system operation condition period is improved by 0.22 percent compared with the SEGS VI power station. Therefore, the invention adopts the method of heating by regions, and can effectively improve the total efficiency of the system.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (7)

1. A design method for a heat collection field of a zoned trough type solar thermal power generation system is characterized by comprising the following steps:
s1 a heat collection field in the trough type solar thermal power generation system supplies heat to a working medium in a heat exchanger through a heat transfer medium, and the heat exchanger is divided into a superheater, an evaporator, a preheater and a reheater; the heat collection field is divided into 3 areas: the system comprises a high-temperature region heat collection field, a medium-temperature region heat collection field and a low-temperature region heat collection field, wherein the high-temperature region heat collection field supplies heat for a superheater and a reheater, the medium-temperature region heat collection field supplies heat for an evaporator, and the low-temperature region heat collection field supplies heat for a preheater; establishing a simulation analysis model of the trough type solar thermal power generation system according to the arrangement mode;
s2 analysis model according to simulation, with Mo＝[Mo,1,Mo,2,Mo,3]As decision variables, an objective function with the maximum total efficiency of the power generation system as an optimization target is established as follows:
minf(MO)＝1-ηA(MO)＝1-ηth(MO)*ηhe(MO)
wherein M iso,1,Mo,2,Mo,3The mass flow of the heat transfer medium in the high-temperature zone heat collection field, the medium-temperature zone heat collection field and the low-temperature zone heat collection field respectively; etaAFor the total efficiency of the power generation system, ηthFor the efficiency of the heat collecting field, ηheThe efficiency of thermoelectric conversion;
s3, under the condition that preset constraint conditions are met, solving the objective function by an interpolation method to obtain heat transfer medium parameters, wherein the constraint conditions comprise heat transfer medium temperature constraint, energy conservation constraint and heat transfer medium mass flow constraint; and then the quantity and the layout mode of the heat collectors in the heat collecting fields of all the areas are obtained according to the parameters of the heat transfer medium, and the design of the heat collecting fields of the trough type solar thermal power generation system is completed.
2. The method of designing a zoned trough solar thermal power generation system heat collection field of claim 1, wherein the heat transfer medium temperature constraints are:
Figure FDA0002606130620000011
wherein, To,i,outFor the i-th zone heat collection field outlet heat transfer medium temperature, To,i,inFor the i-th zone collector inlet heat transfer medium temperature, To,i,ave,minAnd i is the minimum value of the average temperature of the heat transfer medium in the ith area, wherein i is 1,2 and 3.
3. The method of designing a zoned trough solar thermal power generation system heat collection field of claim 1, wherein the energy conservation constraint is:
Figure FDA0002606130620000022
wherein M iso,iFor the ith zone mass flow rate of heat transfer medium,
Figure FDA0002606130620000023
Δ T is the specific heat capacity of the heat transfer mediumo,iThe temperature difference, eta, of the heat transfer medium at the inlet and the outlet of the ith zone heat collectorv,iThe heat exchange efficiency corresponding to the ith area; ms,iThe mass flow of the working medium corresponding to the ith area; Δ hs,iThe enthalpy of the working medium corresponding to the i-th zone increases, i is 1,2, 3.
4. The method of designing a zoned trough solar thermal power generation system heat collection field of claim 1, wherein the heat transfer medium mass flow constraints are: 0<Mo,i≤Mo,maxWherein M iso,iFor the i-th zone heat transfer medium mass flow, Mo,maxThe maximum value of the mass flow of the heat transfer medium which occurs during operation is 1,2, 3.
5. The method of claim 1 wherein the parameters of the heat transfer medium include mass flow of the heat transfer medium in the high temperature zone, the medium temperature zone, the low temperature zone, and the temperature of the heat transfer medium at the outlet of each heat exchanger.
6. The method for designing a heat collection field of a zoned trough-type solar thermal power generation system according to claim 1, wherein in S3, the method for calculating the number of collectors in each zone heat collection field specifically comprises the following steps:
(1) calculating the temperature difference delta T of the heat conduction oil at the outlet and inlet of the heat collection field of the ith area according to the obtained parameters of the heat transfer mediumo,iFurther obtaining the temperature difference delta T of heat conducting oil at the inlet and the outlet of each heat collector of the heat collecting field in the areao,ijAnd the temperature drop delta T of the heat collector connecting pipeo,s,ij(ii) a Then obtaining the number of the collectors connected in series in a single row of the ith area
Figure FDA0002606130620000021
(2) According to the firstRated input power W of heat collector required by i areasth,iThermal power delta W of rated output of single-loop heat collectorth,iPower heat loss delta W of connecting pipe with single heat collectorth,p,ijTo obtain the parallel number of the heat collector circuits of the ith area
Figure FDA0002606130620000024
(3) Calculating the number n of heat collectors in the ith area heat collection fielda,i＝ns,inp,iThe total number n of the heat collectors in the whole heat collection fielda＝∑na,i，i＝1,2,3。
7. The method for designing a heat collection field of a zoned trough-type solar thermal power generation system according to any one of claims 1 to 6, wherein in step S3, when determining the layout of the heat collection field, the total area of the heat collection field is determined according to the total number of collectors in the whole heat collection field and the type of collectors used; if the total area of the heat collecting field exceeds 400000m2If the total area of the heat collecting field is less than 400000m, the heat collecting field adopts an H-shaped arrangement mode2And the heat collecting field adopts an I-type arrangement mode.
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